lol you’re being very dramatic, it could absolutely be done in a garage. Legacy orgs are held together with billions of dollars worth of last minute fixes and duct tape in the US
since I've founded banks over here in Europe, I can tell you: NO! Thats nothing that you could do in a garage :)
Even a PSP requires some "minium/fixed setup" on different layers in the org, so building this with two people over your spring break will not be possible.
